This invention relates to the recovery of heavy crude oil and tar sand oil (bitumen) from underground formation. Locations exist throughout the world with very large reserves of heavy crude oil and tar sand oil but as yet the recovery of heavy crude oil and tar sand oil or bitumen therefrom has not been commercially successful. For example, vast resources of bitumen are present in the oil sands of Northern Alberta, Canada and various techniques have been developed and employed to exploit these resources. As yet, however, the techniques employed have not been completely satisfactory.
Heavy crude oil and tar sand oil (bitumen) are petroleum or petroleum-like liquids or semi-solids naturally occurring in porous media. Tar sand is also called oil sand and bitumenous sand. These materials, heavy crude oil and tar sand oil, may be characterized by viscosity and density. The measure of viscosity has been proposed and used to define heavy crude oil and tar sand oil and density (API gravity) has been proposed and used to define such materials where viscosity measurements are not available. Heavy crude oil has been defined as having a gas-free viscosity of 100-10,000 mPa.s (centipoise) inclusive at original reservoir temperature or a density of 934 kg/m.sup.3 (20.degree. API gravity) to 1000 kg/m.sup.3 (10.degree. API gravity) inclusive at 15.6.degree. C. (60.degree. F.) at atmospheric pressure. Tar sand oil has been defined as having a gas-free viscosity greater than 10,000 mPa.s at original reservoir temperature or a density greater than 1000 kg/m.sup.3 (less than 10.degree. API gravity) at 15.6.degree. C. (60.degree. F.) at atmospheric pressure.
The production and recovery of heavy crude oil from underground formations containing the same has long been practiced but, as indicated hereinabove, the results have not been completely satisfactory, see for example U.S. Pat. Nos. 1,651,311, 2,813,583, 2,875,831, 3,107,726, 3,279,538, 3,490,532, 3,913,671, 4,114,690, 4,223,730, 4,441,555, 4,475,592, 4,487,262, 4,523,642 and 4,660,641. Of interest also with respect to the production of heavy crude oil and tar sand oil, reference is made to the article "Enhanced Recovery of Crude Oil" by T. M. Doscher, American Scientist, Vol. 69, March-April 1981, pp. 193-200, the article entitled "CO.sub.2 Recovery of Heavy Oil: Wilmington Field Test" by W. B. Saner and J. T. Patton, Journal of Petroleum Technology, July 1986, pp. 769.varies.776, and the article entitled "New Production Techniques for Alberta Oil Sands" by M. A. Carrigy, Science, Vol. 234, Dec. 19, 1986, pp. 1515-1518. The disclosures of the above-referred patents and articles are herein incorporated and made part of this disclosure.
It is an object of this invention to provide a method for the recovery of heavy, difficult-to-recover petroleum and bitumenous materials from porous underground formations containing the same.
It is another object of this invention to provide an improved technique for the recovery of tar sand oil or bitumen from underground formations containing the same, such as recovery of tar sand oil from the oil sands located in Northern Alberta, Canada, the so-called Canadian oil sands.
It is yet another object of this invention to provide an improved technique employing readily available materials, such as water and caustic, for the recovery of tar sand oil from tar sands and the like or for the recovery of heavy crude oil or bitumenous materials present in underground porous formations.